The description proceeds from a headlamp and a circuit assembly for simulating a load current from an on-board network, of the generic type disclosed in the main claim.
In recent times, LED-based retrofit lamps have conquered extensive areas of the lighting technology sector, particularly in the field of general lighting. However, retrofit lamps are also increasingly to be found in the automobile industry, where they are intended to, and are capable of replacing the filament lamps employed in this sector. These retrofit lamps have two major advantages: firstly, they are significantly superior to related filament lamp-based items, in terms of energy saving. Secondly, they have a significantly longer service life than the original lamps. Specifically, however, the first advantage results in practical problems in an automobile context, as state-of-the-art vehicles incorporate a monitoring function for filament lamps. This customarily monitors two factors: firstly, with the light in the switched-off state, the resistance of the filament is measured, and it is thus established whether the filament lamp is still functional. Moreover, with the corresponding lamp in service, the current in the lamp is measured. If the resistance exceeds a reference value, or if the current is lower than a reference value, the corresponding line is switched-out, and the on-board computer notifies the driver that the lamp concerned is defective and requires replacement.
Accordingly, the simple replacement of a filament lamp with a retrofit lamp in vehicles of this type is not possible. In headlamps in particular, lamps for key light functions such as dipped beam lighting and main beam lighting are standardized, wherein the associated standard is tailored to filament lamps. This means that LED retrofit lamps cannot be employed in this context, as the headlamp would otherwise lose its approved status.
In order to resolve this problem, replacement headlamps are known, in which standardized light functions are delivered by means of permanently-installed LED lamps or HID lamps. However, even in low-energy replacement headlamps, the problem with the on-board computer remains.